Dermatology Images for the USMLE: Exam Questions and Preparation
How Dermatology are tested on the USMLE, the findings to know, a preparation approach and original practice questions with explained answers.
Dermatology questions often show or describe a skin finding, so the vocabulary of morphology is your toolkit. Once you can name the lesion, the pattern and the distribution, the diagnosis usually follows.
Image-based questions appear on every Step: an ECG tracing, a radiograph, a photograph of the skin, a view of the retina, or a microscopic slide. The skill is the same each time: describe what you see in a fixed order, name the finding, then use it to answer the clinical question. This site does not host exam images, so each finding below is described in words, as many exam stems also do. Practice with an image-rich question bank and the official USMLE sample items to build your pattern recognition. The practice questions here are original and are not real exam items.
How Dermatology is tested
Questions ask for the diagnosis, the confirmatory test or the first-line treatment. Skin findings that signal systemic disease or a drug reaction are tested as well.
High-yield topics
- Primary and secondary lesion terms: macule, papule, plaque, vesicle, bulla, pustule and scale
- Skin cancer: melanoma features, basal cell carcinoma and squamous cell carcinoma
- Inflammatory disease: psoriasis, atopic dermatitis, contact dermatitis and lichen planus
- Blistering disease: pemphigus vulgaris and bullous pemphigoid
- Drug reactions: Stevens-Johnson syndrome and toxic epidermal necrolysis
- Skin infections and infestations: cellulitis, impetigo, tinea and scabies
- Skin signs of systemic disease
Preparation approach
- Describe each lesion by type, color, border, surface and distribution before guessing the diagnosis.
- Compare look-alike diseases in tables, such as pemphigus and pemphigoid.
- Memorize the melanoma warning signs and the next step for a suspicious lesion.
- Review a large set of images, since recognition is learned by seeing many examples.
Practice questions
Question 1
A patient has flaccid blisters and erosions of the skin and mouth, and a positive Nikolsky sign. Which immunofluorescence finding is expected?
- A. Linear IgG along the basement membrane
- B. IgG deposits between keratinocytes in a net-like pattern
- C. Granular IgA in the dermal papillae
- D. Granular IgG along the dermal-epidermal junction
- E. No immunoreactant deposits
Answer: B. This is pemphigus vulgaris, caused by antibodies against desmoglein. Biopsy shows acantholysis and IgG deposits between keratinocytes.
Question 2
A woman has an 8-mm pigmented lesion on her back with asymmetry, an irregular border and variegated color. What is the most appropriate next step?
- A. Observation for 6 months
- B. Cryotherapy
- C. Excisional biopsy with narrow margins
- D. Topical corticosteroids
- E. Shave biopsy and wide excision at the same visit
Answer: C. A suspicious pigmented lesion needs a full-thickness excisional biopsy with narrow margins, so that depth can be measured to guide the definitive treatment.
Question 3
A man has well-demarcated erythematous plaques with silvery scale on the elbows and knees and pitting of the nails. What is the most appropriate initial treatment for limited disease?
- A. Oral prednisone
- B. Topical corticosteroids
- C. Oral antibiotics
- D. Topical antifungal cream
- E. Systemic methotrexate
Answer: B. This is plaque psoriasis. Topical corticosteroids, often with a vitamin D analog, are first-line for limited disease.
Make it a plan
Add a short daily image block to your study routine. See our Step 1 and Step 2 CK preparation timelines for schedules and weekly milestones. This article is general educational guidance and not an individualized study plan.
Educational content only. Confirm current exam requirements with USMLE.